I think it's just the cost. The Spica is about the smallest rocket that could get a human past the Karman line. It's 12m high and weighs 4000kg. To get into orb

I think it's just the cost. The Spica is about the smallest rocket that could get a human past the Karman line. It's 12m high and weighs 4000kg. To get into orbit, you'd need something around the size of the Mercury/Atlas rocket, which was 120,000 kg to get a 1500kg capsule to orbit. Of course, they could do an unmanned mission. The smallest orbital rockets are about 10m tall and 2.5T, for a payload in the 5-10kg range. But I think that is not as interesting for them.